Module 'functools' has no attribute 'cached_property'

[diogobaeder]

Note: if you are reporting a wrong signature of a function or a class in
the standard library, then the typeshed tracker is better suited
for this report: https://github.com/python/typeshed/issues

Please provide more information to help us understand the issue:

• Are you reporting a bug, or opening a feature request?
  Reporting a bug.

• Please insert below the code you are checking with mypy,
  or a mock-up repro if the source is private. We would appreciate
  if you try to simplify your case to a minimal repro.
  from functools import cached_property

• What is the actual behavior/output?
  mypy check error: Module 'functools' has no attribute 'cached_property' - the code however runs just fine.

• What is the behavior/output you expect?
  That mypy succeeds with that line, instead of failing, since the attribute does exist.

• What are the versions of mypy and Python you are using?
  mypy 0.770, CPython 3.8.3

• Do you see the same issue after installing mypy from Git master?
  Yes.

• What are the mypy flags you are using? (For example --strict-optional)
  No flags.

[JelleZijlstra]

This was fixed in #3439, which was released by mypy a while ago. Are you running mypy with --python-version 3.8? functools.cached_property didn't exist before 3.8.

[diogobaeder]

Ah, interesting, that works! I was not specifying the minor version, why is that necessary? Does mypy imply some other minor version if I don't specify it?

[hauntsaninja]

Could you share the command you're running? mypy doesn't allow you to specify only the major version. If you don't specify anything, mypy will use the version of sys.version_info, aka whatever Python you're using to run mypy.

[hauntsaninja]

Closing, as I believe there aren't any changes to be made on typeshed's side — but feel free to post / reopen if you're still having trouble!

[diogobaeder]

Hi @hauntsaninja , I tried with the argument suggested by @JelleZijlstra and it worked. It's surprising that even running it under Python 3.8 requires me to provide that argument, but IMO that's not a big issue, provided that it works I'm fine with that.

Cheers!